The invention relates to a lumbar support, a control device for controlling a lumbar support, a method for controlling a lumbar support and a data carrier on which a program is stored for carrying out a lumbar support control.
The use of supports for motor vehicle seats which can be shaped according to anatomical specifications is continuing to rise. Apart from supports which enable the thighs to be supported without too much pressure, so-called lumbar supports are of particular importance. Through the preferred forward bent posture of the seated occupant the natural forwardly directed concave shape of the spinal column becomes replaced by a substantially convex rearwardly curved shape so that apart from a more rapid onset of fatigue there is also an undesirable deformation of the spinal discs. In order to avoid this undesirably bad posture motor vehicle seats are fitted with lumbar supports. Lumbar supports of this kind should be designed vertically adjustable in order to adapt to the different back lengths and thus different heights of the lumbar support. Normally such lumbar supports are covered with a padding of the vehicle seat. This padding is for this purpose filled, for example, with foam.
Different technical styles of lumbar supports are known. One form comprises an inflatable cylinder provided in the region of the lumbar of the user. This pneumatic lumbar support adjustment is known for example from U.S. Pat. No. 4,655,505. Several air chambers can be governed in sequence through corresponding valves and the pressure in the air chambers can be reduced by means of an outlet valve or can be raised through a pump assembly and measured by means of a pressure sensor.
A further lumbar support is designed so that two parts connected together can be moved up to or away from each other along a guide. A variable curvature is not possible so that a support of the lumbar support is only provided in the narrow region of the highest position so that only one or two vertebrae are supported. A lumbar support of this kind is described by way of example in WO 95/19123.
A further embodiment of lumbar support has a substantially flat surface area support part, with the faces either having apertures or individual support elements arranged side by side which where necessary are designed to taper outwards from the middle. This flat surface support part can be moved with its two end areas up towards each other so that a curvature thereof can be achieved. A desired asymmetric shape, corresponding substantially to a lumbar support can be achieved through variable thicknesses according to EP 0 698 360 B.
The lumbar supports described above are as a rule connected to a frame, for example of the backrest of the vehicle seat. Here the support part of the lumbar support is connected for example to a further frame which has two outer supports running parallel to the spine and along which slide elements can be moved or on which cross supports for the curving support part are fixed in position.
From WO 95/19123 a lumbar support is known which has no support part which can be curved but two arms which are attached to each other for articulated movement. The ends of the arm parts can be moved towards each other and the other ends are connected through a rail having two cylindrical sockets.
Apart from a manual adjustment of such lumbar supports, also called backrest devices, electrically or pneumatically adjustable lumbar support adjusting devices are known which enable an electrically controlled adjustment of the desired shape. These electrically controlled adjusters are operated for example by a button or switch. The adjustment in the case of the said lumbar supports is bound up with the mechanical configuration thereof.
An electric control of a lumbar support adjusting device of this kind is known from DE 43 13 757 A1 and U.S. Pat. No. 5,243,267. This enables, apart from the manual control of the desired support position, a massaging effect to be obtained in that a motor repeatedly and periodically generates a forward and backward movement of the lumbar plate within a predetermined time interval. For a special massaging effect the motor in U.S. Pat. No. 5,243,267 is controlled in a stepped operation. The motor is thereby connected to the supply voltage in dependence on the values of a Fourier sequence in one or other direction in certain time intervals with corresponding polarity and switched on and off to generate a massaging movement.